﻿<p>The profile <em>IfcCenterLineProfileDef</em> defines an arbitrary two-dimensional open, not self intersecting profile for the use within the swept solid geometry. It is given by an area defined by applying a constant thickness to a centerline, generating an area from which the solid can be constructed.</p>

<p>Among else, <em>IfcCenterLineProfileDef</em> is used to model cold-formed
steel or aluminium sections (Sigma, Zeta, Omega, and similar sections
which are not covered by subtypes of <em>IfcParameterizedProfileDef</em>).
However, since <em>IfcCenterLineProfileDef</em> does not provide shape parameters
except for the thickness, there is generally a need to further specify the
profile definition by means of</p>
<ul>
  <li>the name,
  <li>external reference to a document or library,</li>
  <li>profile properties,</li>
</ul>
<p>or a combination of them.  See <em>IfcProfileDef</em> for guidance on external references for profiles.</p>

<blockquote class="history">
HISTORY&nbsp; New entity in IFC2x3.
</blockquote>

<p class="spec-head">Informal Propositions:</p>
<ol>
  <li>The <em>Curve</em> has to be an open curve.</li>
  <li>The <em>Curve</em> has to be a non-intersecting curve.</li>
</ol>

<p>Figure 2 illustrates the center line profile definition. The <em>Curve</em> is defined in the underlying coordinate system. The underlying coordinate system is defined by the swept surface that uses the profile  definition. It is the xy plane of: </p>
      <ul>
        <li><em>IfcSweptSurface.Position</em></li>
      </ul>
<p>The <em>Curve</em> attribute defines a two dimensional open bounded curve. The <em>Thickness</em> attribute defines a constant thickness along the curve.</p>

<table>
<tr><td><img alt="center line" src="../../../figures/ifcarbitraryprofiledef-layout4.gif" border="0" height="300" width="400"></td></tr>
<tr><td><p class="figure">Figure 2 &mdash; Centerline profile</p></td></tr>
</table>